The ‘fiver’: Germanic ‘finger’, Balto-Slavic de-numeral adjectives in *-ero- and their Indo-European background
by Marek Majer (Harvard University)
Proto-Germanic *fingraz ‘finger’ – long connected to PIE *penkʷe ‘5’, but without a convincing derivational scenario – can be interpreted as *pēnkʷ‑ró‑, a genitival R(V̄)‑ó‑ vr̥ddhi derivative to *penkʷerom ‘set of 5’. This latter form is the substantivization of *penkʷero‑ ‘5‑fold, counting 5’ – a form belonging to a series of de-numeral adjectives which, it is argued, is the single type underlying the Baltic pluralia tantum numerals (Lith. penkerì ‘5.pl.tant’) and the Slavic collectives and distributives (PSl. *pętero ‘group of 5’, *pęterъ ‘5‑fold’).
It is further hypothesized that (Post-)PIE forms like *penkʷero‑, *sweḱsero‑, *septm̥mero‑ need not rest upon false segmentation of a thematic derivative of ‘4’ (*kʷetwer‑o-), as is most commonly assumed; rather, they can be explained as simple thematic derivatives of an *‑er locative of the type *penkʷer ‘in/on/at 5’ = ‘in a group of 5’ (a close parallel of this semantic relationship is provided by Lith. trisè ‘3.loc’ = ‘in a group of 3’, or even by French à trois). The posited type *penkʷer also yields a back-formed substantive *penkʷōr ‘set of 5‑s’, a possible source of the Tocharian B distributive numerals in ‑ār (piśār ‘by 5‑s’ << *penkʷōr‑en, *penkʷōr‑i or similar), which – being athematic, cannot be explained via the standard theory starting from *kʷetwer‑o-.