Did he live here? Cause if he did, this could explain some of it: Polish is almost a shortcut to many Slavic languages, especially if augmented with Russian. With only limited exposure, I can understand quite a bit in Czech, Slovak, Croatian, and Ukrainian. Latin and Greek were near-compulsory in Polish schools up until WWII, which lead to weird anecdotes like my grandfather hearing exitus acta probat before some hick tried to beat him up in what you'd call 'the boonies'. German... he could have been exposed to it, depends on where he lived. Lithuanian is a mystery, though, again, it'd depend on his location or travel.
My family history is a massive Eastern European disaster. He was probably raised in Lithuania but we're not super sure. Last names on that side are clearly Americanized versions of Eastern European names so it's essentially impossible to trace back with any efficacy.
