"to strike violently," 1640s, perhaps of Scandinavian origin (cf. Swedish basa "to baste, whip, flog, lash," Danish baske "to beat, strike, cudgel"), from O.N. *basca "to strike;" or the whole group may be independently derived and echoic. Figurative sense of "abuse verbally or in writing" is from 1948. On a bash "on a drunken spree" is slang from 1901, which gave the word its sense of "party."