didn't know squat about

Robert B.Parkerの "Sixkill" を読んでいます。
"Insurance on Jumbo," Morrison said.
"Life insurance?" I said.
"Sort of," Morrison said. "With the production company as beneficiaries, in case Jumbo died or became disabled before he finished the film."
"Don't most movies have some kind of completion insurance?" I said.
"Of course," Morrison said. "But the poor dope didn't know squat about the business. He was just trying to sell insurance."

"didn't know squat about" の個所が分かりません。意味を調べます。
"squat" の項で次の説明がありました。
・Collins Dictionary: anything: used in a negative construction signifying “nothing or a very small amount”: he doesn't know squat about it
・Cambridge English Dictionary: anything: he shouldn't talk - she doesn't know squat about it.

Oxford English Dictionaryでは "diddly-squat" の項で説明と例文をあげていました。
informal usually with negative: Anything.: she didn't care diddly-squat about what Darryl thought; they don't know diddly about softball

運動の "squat" はほとんど毎日していますが、こんな意味・表現があるのは知りませんでした。