To take heed of or to have caution.
To have care or concern (for) or take heed (of)
He recks not of the peril.
To concern or be of concern; matter (to)
It recks him not.
Origin of reck
From Middle English recken, rekken, reken, from Old English rÄ“ccan, rÄ“can, from Proto-Germanic *rÅkijanÄ… (“to care, take care"), from Proto-Indo-European *rÄ“Çµ-, *rÄ“g- (“to care, help"). Cognate with Low German roken, ruken (“to reck, care"), German geruhen (“to deign, condescend"), Icelandic rÃ¦kja (“to care, regard, discharge"), Danish rÃ¸gte (“to care, tend").