'reliably-stocked' originates from English as a hyphenated compound, combining the adverb 'reliably' (from 'reliable' + '-ly') with the past participle 'stocked' of the verb 'stock.' 'Reliable' is formed from 'rely' + '-able,' while 'stock' traces back to Germanic roots.

'reliably' developed in Modern English from 'reliable,' and 'stocked' is the participial form of 'stock,' a word descending from Old English 'stocc' (“tree trunk; post,” later “supply, store”). These elements were combined in modern usage to form the attributive compound 'reliably-stocked'.

Initially, it meant “stocked in a manner that can be relied upon,” and it retains essentially the same meaning in current usage, especially in retail and supply-chain contexts.