IPA: /ˈtɪndərˌbɒks/
KK: /ˈtɪndərˌbɑks/
A container made of metal used to hold tinder and often includes tools like flint and steel to start a fire.
The campers packed a tinderbox to ensure they could start a fire easily in the wilderness.
Tinderbox is formed from "tinder" (from Old English *tyndre*, meaning a material used to catch fire) and "box" (from Old English *box*, meaning a container). A tinderbox is a container used to hold tinder for starting a fire.
Think of a 'container' ('box') that holds 'material for fire' ('tinder') — that's what a tinderbox is used for.