蜡

Left insect radical — the indexing radical. Anchors 蜡 in the bug family alongside 蜂 bee, 蚁 ant, 蝶 butterfly. Originally beeswax — the substance secreted by bees from their abdomens — gave 蜡 its first meaning, hence the insect tag. From beeswax the meaning generalised to all wax: candle wax, sealing wax, paraffin.

Right 昔 supplies the sound, drifting from xī to là through an older phonetic series. The 'former times' sense plays no part in the meaning; pure sound peg here. Same phonetic powers 借 to borrow, 错 wrong, 措 to arrange, 醋 vinegar — all sharing different reflexes of the same root.