"a heavy blow," 1805, from bash (v.). Meaning "an attempt" is attested by 1945. On a bash "on a drunken spree" is slang from 1901, which gave the word its sense of "a wild party."
Turkish honorary title formerly given to officers of high rank, 1640s, from Turkish pasha, also basha, from bash "head, chief" (no clear distinction between -b- and -p- in Turkish), from Old Persian pati- "master" (from PIE root *poti- "powerful; lord") + root of shah. Earlier in English as bashaw (1530s).