Mehri

hədhōm - to have sexual intercourse with one’s wife at night when another (us. a young child) is in the sleeping area (ML 66)

May eventually be related to the present root with unusual semantic derivations from ‘dark, darkness’ (cf. Bulakh 2006a, 198f.). See also dəhōm ‘heat-haze, shimmer’ (ML 66).

PS
*dhm - to be dark (Fronzaroli 1965a: 138–139, 145, 149; Kogan 2011: 196; EDA II)

One cannot exclude that Hbr. nidhām “astounded, confused” (HALOT 214) belongs to this root with a metaphoric shift of meaning (< “dark, gloomy”, сf. Russian мрачный). Admittedly, the context of the only passage where it is attested (Jr 14:9) rather suggests the meaning “helpless”.