'aulder' originates from Scots, specifically the word 'auld' with the comparative suffix '-er', where 'auld' derived from Old English 'eald' meaning 'old'.

'aulder' changed from the Scots adjective 'auld' (from Middle English auld/aulde) and ultimately from Old English 'eald', and developed the comparative form 'aulder' in Scots dialect.

Initially it meant 'old' (via 'auld'/'eald'), but as a comparative form it evolved to the current meaning of 'older'.