-issimus

Etymology
Via, from (zero-grade of ) +. The latter is seen whole in -timus (e.g. –,  – , assimilated  – ). The original form seems, however, to be (cf.  –, Gothic ), with acquired t from the paradigm -ter- – -timus- (e.g.  – ), and is cognate with 🇨🇬 (source, via metanalysis, of English ). By various sound changes (e.g. *-isemos > *-ismos > -īmus) superlative grades in -īmus, -ēmus etc. (e.g., ) are also found.

The expected alteration of *-(o)ism̥mos to *-erimus is nowhere to be found. The -ss- may be an example of expressive lengthening of the *-s- or influence from specific forms as pessimus and endings in -errimus and -illimus.

Usage notes

 * Stems in -ro- and -lo- instead take the suffix and  respectively (e.g. *polkros  > *polkrisemos > *polkr̥semos > *polkersimos > ).
 * Some adjective nouns have irregular superlative grades from other roots or compositions (e.g. –,  – ,  – ).