'unalterably-split' originates from the combination of 'unalterably' and 'split'. 'Unalterably' comes from the prefix 'un-' meaning 'not', and 'alterably' from 'alter' meaning 'to change'. 'Split' comes from Middle English 'splitten', meaning 'to divide'.

'Unalterably' evolved from the Latin 'alterare', meaning 'to change', combined with the prefix 'un-' to denote negation. 'Split' evolved from the Middle English 'splitten', which was derived from the Old Norse 'splita'.

Initially, 'unalterably' meant 'in a way that cannot be changed', and 'split' meant 'to divide'. Together, they convey a sense of permanent division.