Reconstruction:Proto-Slavic/-slo

• *-slь, *-sla
• *-lo
• *-dlo (after vowels or r/l)

From Proto-Balto-Slavic *-sla(s). Probably from *(s)-tlo, from *(d/t/s/z)-tlo, from Proto-Indo-European *-tlom.

Inherited, but becoming productive only in Proto-Slavic. There are many direct cognates, e.g.

• *veslo (“oar, paddle”) = Latin vēlum (“sail”)
• *čerslo = Lithuanian ker̃slas (“tool for drawing blood”)
• *krěslo = Lithuanian krė́slas

Exact match to *-lo and *-slo are Lithuanian -las and -slas, forming instrument nouns as well as action nouns (> nomina acti).

*-slo n

1. Deverbal, forming nouns denoting a tool or instrument.

   *vezti (“to lead, cart, convey”) → *veztlo/*vezslo > *veslo (“oar, paddle”)

   *mazati (“to smear, anoint”) → *maztlo/*mazslo > *maslo (“oil, ointment”)

2. (rare) Deverbal, creating action nouns, usually becoming nomina acti.

   *čitti > *čisti (“to read; respect”) → *čittlo/*čitslo > *čislo (“number”)

• Used with verbs ending -C- or -a/j-
• Usually used with verbs with e-vocalism of the root.
• Usually from roots ending in d/t/s/z. It's not used with roots ending in r/l (see *-dlo). Possibly *-lo is used with roots ending in b/p/k/g.

• *-sno
• *dolto

• Šekli, Matej (2012) “Besedotvorni pomeni samostalniških izpeljank v praslovanščini”, in Philological Studies‎^[1] (in Slovene), volume 10, number 1, Skopje, Perm, Ljubljana, Zagreb, pages 115–32
• Trubachyov, Oleg, editor (1985), “*kreslo / *krěslo”, in Этимологический словарь славянских языков [Etymological dictionary of Slavic languages] (in Russian), numbers 12 (*koulъkъ – *kroma/*kromъ), Moscow: Nauka, page 126
• Sławski, Franciszek, editor (1974), “*-slo”, in Słownik prasłowiański [Proto-Slavic Dictionary] (in Polish), volume 1 (a – bьzděti), Wrocław: Ossolineum, page 103
• Rainer Eckert (1972) “Возможные отражения древнего корня *ou̯əd- (ср. лит. áusti 'ткать') в праславянском языке”, in Этимология 1970, Moscow, page 46
• Oleg Trubachyov (1963) “Формирование древнейшей ремесленной терминологии в славянском и некоторых других индоевропейских диалектах”, in Этимология: Исследования по русскому и другим языкам, Moscow: USSR Academy of Sciences Publishing House, page 34