calamitas.

According to Schrijver, probably built from an unattested adjective *calamis or *calamus + -tās. This same base adjective is probably also continued by incolumis. According to this theory, the second syllable was not syncopated due to the influence of the adjective from which it derived. Schrijver connects this adjective to the root Proto-Indo-European *kelh₂- (“to beat”), suggesting perhaps a pre-form of the shape *kelh₂-mo-, which would yield *kela-mo- with the vocalization of the laryngeal and eventually *cala-mo- with a sound change of *e > *a after a pure velar (compare also scandō (“to jump”) for a possible example of a similar development). Regarding the ablaut grade of this PIE adjective, Schrijver compares Ancient Greek θερμός (thermós, “warm”) (< *gʷʰer-mo-s). Alternatively, Schrijver suggests that it may reflect an *m-stem adjective of the shape *kl̥h₂-em-, though he concedes that there are no other known adjectives of this type. However, terms of a similar structure are attested in nouns, such as Ancient Greek κάλαμος (kálamos, “reed”). This second proposal is supported by De Vaan, who considers there to be no other good explanation for the initial ca-. An old form by l-d-alternation is Old Latin kadamitās.