THE sweetest and most fluent cussing that ever cut the Massachusetts air is gone forever because the lovely place that spawned it has closed its doors.

"Kings Tavern," 30 Boylston St., the last men-only bar in the Harvard area, was locked up on Christmas Eve after 32 years as a haven for men whose consuming passion was to find a refuge from their women.

"I loved to go in there and swear," one old Irishman lamented as he guzzled a beer at Whitney's, across the street, as women lolled around. He is old and getting older, gray on the sides of his head, pate shining like a full moon on top.

"Now I swear a little bit and turn around to see who's looking over my shoulder."

Kings Tavern, which had a cheery sign reading "Men's Bar" hanging outside, has closed up and gone underground. The owner, Nick Harris, has opened a cabaret, spell it cafe, directly underneath the old location, where young girls and bearded students hang out. It's at 30B (for Basement) Boylston, and the old regulars at Kings Tavern feel there's no place there for them.

"I went down there once and that's it," said one grizzled gentleman.

The old Kings Tavern is being remade into "Minuteman Radio" by owner John Waugh, who will have a mod radio and record shop there. It will open about March 1 with a "Hi-Fi Happening."

There is no joy at these tidings among the elderly Irishmen who have been sampling the delights of Kings Tavern's draft beer since it first opened, as the "Essex Lunch," 32 years ago.

The most magnificent master of the swearword who ever inhabited Kings Tavern was a bricklayer who was also an accomplished artist, painting in oils and watercolors. He swore in multi-syllables, interspersed profanity between dictionary words, such as: "This is the most non-Goddamn-son-ofabitching-sensical suggestions I ever heard of!" Nobody since Joseph Pulitzer Sr., who invented multi-syllable swearing, had heard such poetic loquacity.

This same bricklayer-artist had a five-year-old daughter, a precocious lass who was already her father's equal and was bidding for the championship.

When they were invited to dinner at a friend's house one time, the father sternly warned the five-year-old prodigy: "Now you keep your mouth clean."

They all sat down to dinner and the daughter, after sampling the food, announced: "I can't eat this shit!"

The bricklayer-artist turned to his host and said:

"What did I tell you, it's this fucking neighborhood we live in."

THE MEN'S bar always opened at 8 a.m. and closed at midnight; it was most popular among harried males who needed a bit of the hair of the dog and no questions asked.

Not that the place wasn't one oferuditeness and respectability. Once two Harvard professors were sipping a beer in the Kings Tavern and arguing about the Etruscan Wars.

Our bricklayer-artist, the one with the fluent daughter, listened in patience till his patience was gone. Ultimately he said to one of the professors:

"Excuse me, but he's quite right." The professor who was in error admitted it and drinks were had all around.

Eddie St. Louis, a very large man who once played in the backfield for the Pittsburgh Stealers so long ago that pro football was not a paying proposition-30 or 40 years ago-remembers many a convivial round in the Kings Tavern with Ed Lahey. Lahey was a member of the first Nieman Fellowship Class in 1938. Once in a while Tom LaVelle, one of the seven mules in the line ahead of Notre Dame's immortal Four Horsemen, would join them.

Nick Harris has moved the Kings Tavern, Men's Bar, right down into the basement. Henceforth, it will be called simply "Kings" and it will have queens too, youthful, longhaired lovely young things along with earnest and jolly bearded beer drinkers, an entirely new crowd and altogether foreign to the tastes of the old-timers.

But change, of course, is inevitable, and not wholly evil. Nick Harris is carrying with him the best commodity, after all, of his old place: the draft beer.

The Kings Tavern draft is known far and wide. It is so good that one of United Airlines' brochures urges visitors to be sure to visit Kings Tavern in Harvard Square and sample the draft beer, and newspapers from as far away as San Francisco have printed laudatory articles about the beer.

The secret is the stable temperature-between 38 and 40 degrees-and Nick's insistence that the lines be flushed clean at every changing of kegs.

"As I understand it, when beer hits extremes between hot and cold, it loses the flavor," Nick said. To circumvent temperature changes, all his kegs of beer are stored in a large freezer and the kegs are tapped there, with lines leading into the bar.

The kegs never leave the cooler. The lines are regularly flushed. People seem to like what comes out as a result.

So the new place has the same good cold draft, and the new clientele is contented, and it is only the old guys who grumble, as they crowd in now at Harvard Gardens or Whitney's and wish to God there was one place left on earth where they could get away from the old woman and swear a little and argue one more time about the Etruscan Wars.