[…] "consubstantial Trinity" could have been a reaction against the supposed heresy of […] Damian […] who was accused of "tetratheism" (or "tetradism", distinguishing four different entities in the Godhead), a response to, but as it seems a variant of, the very influential "tritheism" of John Philoponus (distinguishing three Deities in the Trinity) […]
Source: wiktionary