Wurm (1975) placed it as an independent branch of Trans–New Guinea, but Ross (2005) could not find enough evidence to classify it.

Usher (2020) found that it was one of the West Pauwasi languages, though divergent from the other two branches of that family.

[3] An automated computational analysis (ASJP 4) by Müller et al. (2013)[4] found lexical similarities between Usku and Kaure.

However, since the analysis was automatically generated, the grouping could be either due to mutual lexical borrowing or genetic inheritance.

[3] Some of the few documented sentences in Usku are:[3] e3wangmoneyo1SGaifatherseDATroti-mogive-TNSe wang o ai se roti-mo3 money 1SG father DAT give-TNS‘She gave money to my father.’e3kompongvillageseDATrifli-mogo-TNSe kompong se rifli-mo3 village DAT go-TNS‘He went to the village.’kɨnmarpersonkompongvillageeABLduar-mocome-TNSkɨnmar kompong e duar-moperson village ABL come-TNS‘That person came from the village.’kɨnmarpersonmra-mudog-ERG/FOC?ya-mubite-TNSkɨnmar mra-mu ya-muperson dog-ERG/FOC?