An interesting common NC cultural term. We should stress that Lak. ruḳ and PD *duḳ 'yoke', however similar, still belong to another root (see *riḳwV) (although of course the root *ʔrĕg_wĔ could have influenced it). In PWC the root obtained a prefixed labial (a rather frequent development), with a usual in such cases delabialisation of the following consonant. See Trubetzkoy 1922, 241, Abdokov 1983, 131. We will probably be right in separating the root *ʔrĕg_wĔ from a slightly similar cultural Wanderwort, present in many linguistic families of the Near East: IE *i_eug- / *i_ug-, PK *uʁel-, Sem. *ʁull-, the source of which may be ultimately Indo-European (cf. IE *i_eug- 'to bind'). See abundant discussion of this root in Illich-Svitych 1965, 334-335, Goniashvili 1940, 581, Klimov 1964, 186, Deeters 1957, 390. There are traces of this root in NC languages as well: cf. Abkh. a-wǝ́ʁʷ, Ub. ʁawǝ́ (possibly borrowed from Kartvelian, see Charaya 1912, 15; Illich-Svitych ibid.; Shagirov 1,90; however, a reconstruction like PWC *wVGwV is also possible, and the precise direction of loan is still to be determined), Tab. (Kand.) uʁin 'yoke for one ox' (as opposed to jirk:aʁ "yoke for two oxen"). As we see, they are very sparse, and probably represent a later loanword - at any rate, having nothing to do with PNC *ʔrĕg_wĔ.