formerly, a laced boot reaching halfway up the calf or to the knee, e.g. the high thick-soled boot worn by actors in ancient Athenian tragedy

the high thick-soled boot (the cothurnus) worn by actors in ancient Athenian tragedy, often contrasted with the ‘sock’ (soccus) worn by actors in comedy

to hear thy buskin tread and shake the stage — Ben Jonson

tragic drama, esp tragedy resembling that of ancient Greek drama