From Latin 'sēcūrus' (free from care), 'sē-' (without) + 'cūra' (care) — literally 'to make someone without worry.'
To tell someone something positively to dispel doubt; to make certain that something will happen.
From Old French asseurer (to reassure, to make safe, to guarantee), from Vulgar Latin *assecurare, from ad- (to) + securus (safe, free from care), from se- (without, apart from) + cura (care, concern, trouble). The PIE root underlying cura is *kois- (to care for). The literal meaning is to make free from care. The insurance sense — guaranteeing
In British English, 'assurance' specifically refers to life insurance (covering certain events like death), while 'insurance' covers uncertain events (like fire or theft). This distinction, though fading, preserves the word's original meaning — 'assurance' was a guarantee, while 'insurance' was protection against risk.