This thread on StackExchange has a detailed enough explanation of Japrisot‘s (or Rossi‘s) arguably seminal translation error. I don’t quite agree, however, that it was a case of a rare idiom misunderstood. Rather, the phrasal verb to beat off was the root of the problem. If Rossi had gotten it right, he would have figured out the idiom to beat somebody/them off with a stick (already attested, by the way, before Salinger’s birth). Webster 1913 is crystal clear on this verb:
To beat off, to repel or drive back.
The first edition of the Oxford English Dictionary (OED, Volume 1 published 1884) points in the same direction:
Beat off: a. To drive away from by blows, attacks, volleys (cf. 16, 17); b. (see 19).
Looking up (19):
To strive against contrary winds or currents at sea; to make way in any direction against the wind.
The only potentially confusing reference is “cf. 17,” as (17) is “to break, crush, smash, or overthrow by hard knocks; to batter.” Even so, it’s impossible to dispose with “to repel, to drive away” as the most likely meaning. What dictionaries did Rossi use in the early 1950s? Perhaps they weren’t clear or detailed enough on English phrasal verbs.
Anyway, the translator accepted the idea that M. Blanchard, who was “pretty good” according to Holden Caulfield, spent his time beating women and was pretty good at it (“s’y connaissait”). This false start set the tone for the whole paragraph. The club mutated into a cane: now Blanchard was fond of caning women. In line with this premise, “rake” became “sadique,” and the women bloody (“vachement”) liked the treatment. The passage detached itself from the original but gained a certain internal coherence: Blanchard became a practitioner of an alternative lifestyle, a Christian Grey with a likely propensity for edge play. Unsurprisingly, the “lousy book” that spawned Blanchard morphed into a dirty little book. “Jolly good stuff, Swishes,” as Larkin wrote to Conquest.
More that thirty years after Rossi, Annie Saumont translated The Catcher in the Rye anew. Born in 1927, she was a far more experienced translator in the mid-1980s than Rossi had been in the early 1950s. Nevertheless, as the opening link makes clear, she misinterpreted beat off as beat, just as Rossi had done. Unlike him, she didn’t rewrite the whole paragraph for consistency, so it turned out fairly odd: Blanchard passed his time beating women with a golf club; he was un vrai tombeur; and they didn’t resist.
But Annie Saumont wasn’t the only translator Rossi led astray, if my theory is correct. (To be continued.)