|Attestation:||avaśuerasi, esimnesi, esumnesi, kastriesi, kuninasi, laθurusi, lastasi, pitaunesi, ritauiesi, )si, φelturiesi
Corresponding to the Etruscan pertinentive I (Rix 1985: 128, Wallace 2008: 47). Like the ablative, the pertinentive is built with genitive forms / adjectives of possession as base (Rix 1985: 127). The pertinentive is historically a locative to the genitive, hence the complex pertinentive endings reflect both those of genitive and locative (locatiuus genitiui in Eichner's terminology). The pertinentive I is based on the genitive I -s(i), historically -si: -si-i > -si. In this context, auslauting i survived apocope (while being lost in the genitive).
As might be expected, the use of the pertinentive I corresponds to that of the genitive I, i.e. being the preferred allomorph for individual names not ending in a dental fricative.