Slow
Old English slāw ‘slow-witted, sluggish’, of Germanic origin.
wiktionary
From Middle English slow, slaw, from Old English slāw(“sluggish, inert, slothful, late, tardy, torpid, slow”), from Proto-Germanic *slaiwaz(“blunt, dull, faint, weak, slack”), from Proto-Indo-European *(s)lew-(“limp”). Cognate with Scots slaw(“slow”), Dutch sleeuw(“blunt, dull”), Low German slee(“dull, sluggish”), German schlehe, schleh(“dull, exhausted, faint”), Danish sløv(“dull, torpid, drowsy”), Swedish slö(“slack, lazy”), Icelandic sljór(“dim-witted, slow”).
etymonline
slow (adj.)
Old English slaw "inactive, sluggish, torpid, lazy," also "not clever," from Proto-Germanic *slæwaz (source also of Old Saxon sleu "blunt, dull," Middle Dutch slee, Dutch sleeuw "sour, tart, blunt," Old High German sleo "blunt, dull," Old Norse sljor, Danish sløv, Swedish slö "blunt, dull"). Meaning "taking a long time" is attested from early 13c. Meaning "dull, tedious" is from 1841. As an adverb c. 1500. The slows "imaginary disease to account for lethargy" is from 1843.
slow (v.)
1550s, "make slower;" 1590s, "go slower," from slow (adj.). Related: Slowed; slowing. Old English had slawian (intransitive) "to be or become slow, be sluggish," but the modern use appears to be a 16c. re-formation.