Reckless

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Old English reccelēas, from the Germanic base (meaning ‘care’) of reck.

wiktionary

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From Middle English rekles, reckeles, rekkeles, (also recheles), from Old English rēcelēas(“reckless, careless, negligent”), equivalent to reck +‎ -less. Cognate with West Frisian roekeleas(“reckless”), Dutch roekeloos(“reckless”), German Low German ruuklos(“careless”), German ruchlos(“careless, notorious”).

etymonline

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reckless (adj.)

Middle English recheles, from Old English receleas "careless, thoughtless, heedless," earlier reccileas, literally "not recking (of consequences)" from *rece, recce "care, heed," from reccan "to care" (see reck (v.)) + -less. The same affixed form is in German ruchlos, Dutch roekeloos "wicked."

The root verb reck (Old English reccan) is passing into obscurity; the range of Middle English spellings might reflect uncertainty even then about it, e.g. rechiles, retcheles, recelease, richeles, regeles, reccles, rakeles.