Thrall
Old English thrǣl ‘slave’, from Old Norse thræll .
wiktionary
From Middle English thral, thralle, threl, threlle, from Old English þrǣl(“thrall, slave, servant”), from Old Norse þræll(“slave”), from Proto-Germanic *þrahilaz, *þragilaz, *þrigilaz(“runner, gofer, servant”), from Proto-Indo-European *trāgʰ-(“to pull, drag, race, run”); according to ODS probably related to Gothic 𐌸𐍂𐌰𐌲𐌾𐌰𐌽( þragjan), Old English þrǣġan(“to run”). [1]
From Middle English thrallen, from the noun above. Compare Old Norse þræla.
etymonline
thrall (n.)
late Old English þræl "bondman, serf, slave," from a Scandinavian source akin to Old Norse þræll "slave, servant," figuratively "wretch, scoundrel," probably from Proto-Germanic *thrakhilaz, literally "runner," from root *threh- "to run" (source also of Old High German dregil "servant," properly "runner;" Old English þrægan, Gothic þragjan "to run"). Meaning "condition of servitude" is from early 14c.