C19: from the Italian phrase tempo rubato, literally: stolen time, from rubare to rob
rubato in American English
(ruˈbɑtoʊ)
[also in italics]; Music
adjective, adverb
1.
with some notes arbitrarily lengthened (or shortened) in performance and, often, others correspondingly changed in length; (in a manner)intentionally and temporarily deviating from a strict tempo: also used as a musical direction