1) house of roundness, roundhouse, prison 1a) name of a prison
Full Brown-Driver-Briggs lexicon entry
סֹ֫הַרnoun [masculine]roundness (?); — only in ׳בֵּית הַמּGen 39:20 (twice in verse); Gen 39:21; Gen 39:22; Gen 39:23 (all J), Gen 40:3; Gen 40:5 (RJ), the round house (name of a prison: but ׳ס perhaps an Egyptian word Hebraized, compare Dr in HastingsDB ii.768 n. and EbÄg. M. 318 f.).