1748, "having no pulse or heartbeat," from pulse (n.1) + -less. Figurative sense of "devoid of energy or feeling" is by 1856.
Entries linking to pulseless
pulse n.1
"a throb, a beat, a stroke," especially a measured, regular, or rhythmical beat, early 14c., from Old French pous, pulse (late 12c., Modern French pouls) and directly from Latin pulsus (in pulsus venarum "beating from the blood in the veins"), past participle of pellere "to push, drive" (from PIE root *pel- (5) "to thrust, strike, drive").
Extended usages, of feeling, life, opinion, etc., are attested from early 16c. The figurative use for "life, vitality, essential energy" is from 1530s.
-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.