'angulo-splenial' originates from New Latin, specifically combining Latin 'angulus' (from Latin) meaning 'angle' and the element 'splenial' ultimately from Greek 'splēnion' (σπλήνιον) meaning 'a small plate' or 'thin plate'.

'angulo-splenial' was used in New Latin anatomical and osteological descriptions (often as a compound of 'angular' and 'splenial' or forms like 'angulo-splenialis') and eventually entered modern English anatomical terminology as 'angulo-splenial'.

Initially the term referred generally to structures relating to the angular and splenial regions of the lower jaw; over time it came to be used specifically for the fused mandibular element observed in certain fishes and early tetrapods.