late Old English had unfelende, "having no sensation." Middle English had a verb unfeel "be insensible, fail to feel" (early 14c.) as well as unfeelingness "insensibility, loss of sensation," and unfeelingly "without understanding or direct knowledge" (late 14c.), and a verbal noun unfeeling "loss of sensation, lack of feeling." However the word in its main modern meaning "devoid of kindly or tender feelings" is from 1590s, from un- (1) "not" + past participle of feel (v.). Related: Unfeelingly.