"having no motive or aim," 1798, from motive (n.) + -less.
Entries linking to motiveless
motive n.
late 14c., "something brought forward, a proposition, assertion, or argument" (a sense now obsolete), from Old French motif "will, drive, motivation," noun use of adjective, literally "moving," from Medieval Latin motivus "moving, impelling," from Latin motus "a moving, motion," past participle of movere "to move" (from PIE root *meue- "to push away").
Meaning "that which inwardly moves a person to behave a certain way, mental state or force which induces an action of volition" is from early 15c. Hence "design or object one has in any action."
-less
word-forming element meaning "lacking, cannot be, does not," from Old English -leas, from leas "free (from), devoid (of), false, feigned," from Proto-Germanic *lausaz (cognates: Dutch -loos, German -los "-less," Old Norse lauss "loose, free, vacant, dissolute," Middle Dutch los, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart." Related to loose and lease.