An impersonal verb form appearing as N. bui “I must” in The Etymologies of the 1930s, derived from primitive ᴹ✶mauy- under the root ᴹ√MBAW “compel, force, subject, oppress” (Ety/MBAW; EtyAC/MBAW). The gloss “I must” did not appear in The Etymologies as published in The Lost Road (LR/372), but did appear in the Addenda and Corrigenda to The Etymologies (VT45/33).

Neo-Sindarin: In (Neo) Sindarin phonology, the more likely form is ᴺS. boe, as suggested in Hiswelókë’s Sindarin Dictionary (HSD). The general Neo-Sindarin consensus is that this impersonal verb can be used for “must” with the putative subject in the dative and the required action as a verbal noun: boe annin maded “I must eat, (lit.) [it] needs for me to eat”.