Proto-Indo-European root meaning "to let go, slacken."
It is the hypothetical source of/evidence for its existence is provided by: Greek ledein "to be weary;" Latin lenis "mild, gentle, calm," lassus "faint, weary;" Lithuanian lėnas "quiet, tranquil, tame, slow," leisti "to let, to let loose;" Old Church Slavonic lena "lazy," Old English læt "sluggish, slow," lætan "to leave behind."
early 15c., omitten, "fail to use or do, fail or neglect to mention or speak of, to disregard," from Latin omittere "let go, let fall," figuratively "lay aside, disregard," from assimilated form of ob (here perhaps intensive) + mittere "let go, send" (see mission). Related: Omitted; omitting.
"allowable, proper to be allowed," early 15c., from Old French permissible (15c.) and directly from Medieval Latin permissibilis, from permiss-, past-participle stem of Latin permittere "let pass, let go; grant, permit" (see permit (v.)).