rathskeller n.

*rē-, Proto-Indo-European root meaning "to reason, count;" a variant of PIE root *ar-, also arə-, "to fit together." 

It forms all or part of: Alfred; arraign; arithmetic; Conrad; dread; Eldred; Ethelred; hatred; hundred; kindred; logarithm; Ralph; rate (n.) "estimated value or worth;" rathskeller; ratify; ratio; ration; read; reason; rede; rhyme; riddle (n.1) "word-game;" rite; ritual.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit radh- "to succeed, accomplish;" Greek arithmos "number, amount;" Latin reri "to consider, confirm, ratify," ritus "rite, religious custom;" Old Church Slavonic raditi "to take thought, attend to;" Old Irish im-radim "to deliberate, consider;" Old English rædan "to advise, counsel, persuade; read;" Old English, Old High German rim "number;" Old Irish rim "number," dorimu "I count."

early 13c., "store room," from Anglo-French celer, Old French celier "cellar, underground passage" (12c., Modern French cellier), from Latin cellarium "pantry, storeroom," literally "group of cells;" which is either directly from cella "small room, store-room" (from PIE root *kel- (1) "to cover, conceal, save"), or from noun use of neuter of adjective cellarius "pertaining to a storeroom," from cella. The sense "room under a house or other building, mostly underground and used for storage" gradually emerged in late Middle and early Modern English. Related: Cellarer. Cellar-door attested by 1640s.