Remiss

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late Middle English: from Latin remissus ‘slackened’, past participle of remittere . The early senses were ‘weakened in colour or consistency’ and (in describing sound) ‘faint, soft’.

wiktionary

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From Middle English remisse, remysse, from Latin remissus(“languid, negligent”), perfect passive participle of remittere(“remit”).

etymonline

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remiss (adj.)

early 15c., remis, remisse, "weak, dissolved, loose, slack, lacking in force or energy;" mid-15c., of conduct, "characterized by lack of strictness or due restraint;" also, of persons, "slack in the discharge of a task or duty, characterized by negligence," from Latin remissus "relaxed, languid; negligent," past participle of remittere "slacken, abate, let go" (see remit). Related: Remissly; remissness.