Apple pie (Wikipedia)

Pie stuck to a number of phrases, private ones at first and then sentences of ordinary conversation, by slip of the tongue to start with and afterwards defiantly, mixing embarrassment and the refusal to be embarassed. Pie functions as pet name (dear one), as interrogative (are you awake?), as exclamation (how could you say such a thing!).
So near have I approached to that which I vowed I would never use, the edged endearment of the grown-up, the darling of protest if not yet the darling of bitter reproach.
Pie is allied by assonance with my (my Pie), by alliteration with expressive adjectives: poor Pie, precious Pie, pretty Pie.
Occasionally it appears in phrases of estrangement, though its use acts as a guarantee that estrangement is reversible: crusty Pie, poison Pie. piranha Pie.
Written down and rationalized as an irrational number — ? — it loses a little of its sugar. Transported into fake Italian mio Pio — it acquires a register almost operatic. As a double diminutive — as pielet or pilot — it brings into play a fresh set of overtones.

— From Baby Clutch, an essay by Adam Mars-Jones in Granta 27, Summer 1989 issue that carried the theme Death.