'hippocampal-related' is a Modern English compound combining 'hippocampal' (from New Latin 'hippocampus', ultimately from Greek 'hippokampos', where 'hippo-' meant 'horse' and 'kampos' meant 'sea-monster' or 'sea-creature') and 'related' (from Latin via Old French, from the Latin root 'referre/relatus' meaning 'to bring back' or 'to relate').

'hippocampus' came from Greek 'hippokampos' and passed into New Latin as 'hippocampus'; the adjective 'hippocampal' was formed in Modern English from that New Latin stem. 'Related' developed from Latin 'relatus' through Old French and Middle English to modern 'related'. The compound 'hippocampal-related' is a modern formation combining those elements to mean 'related to the hippocampus'.

Originally 'hippokampos' literally referred to a 'seahorse' (and later the anatomical structure was named for that shape); over time the term became the name of a brain structure, and 'hippocampal' came to mean 'pertaining to that structure', so the compound now means 'pertaining to or associated with the hippocampus'.