Quiz: Remember the definition of mal de mer?
"full of loops," 1856, from loop + -y (2). Slang sense "crazy" is attested from 1923. Earlier figurative sense was "cunning, deceitful" (by 1825).
Crazy; silly; nutty: that loopy guy whose handkerchief you cry into/ visually complemented the singer's loopy Balkan bop/ even loopier bids for the few works in Wood's small mature oeuvre (1925+)