Remorseless means feeling no regret, or never letting up. A remorseless rain.
The two senses are quite different, since one is about a person and the other about a process. Remorseless of weather or of pressure means unrelenting rather than cruel.
1adjectiveremorselessFeeling no regret, or never letting up.
“The remorseless noise from the road went on all night.”
remorseless is a quality.
Proto-Indo-European
*(s)merd-
Latin
remordeō — to torment, vex
Medieval Latin
remorsus
Old French
remors
Middle English
remors
English
remorse
English, today
remorseless
From remorse + -less. remorse First attested circa 14th century as Middle English remors, from Old French remors, from Medieval Latin remorsus, from Latin remordeō (“to torment, vex”) literally “to bite back”, from re + mordeō. More at remord.
Etymology from Wiktionary, CC BY-SA