curdle
UK[ˈkɜː.dl̩]US[ˈkɝː.dl̩]
v
(of a liquid, especially milk) to separate into solid and liquid parts, forming lumps.
v
(of blood) to become thick or to clot.
v
(figurative) to fill with fear or horror; to cause to curdle (as in "to curdle the blood").
Etymology
The journey of 'curdle' begins with the Middle English noun 'curd', referring to the coagulated part of soured milk. The exact origin of 'curd' is obscure, but it is linguistically linked to the earlier form 'crud', suggesting a common Germanic root related to coagulation or thickening. The addition of the verbal suffix '-le' transformed it into 'curdle' in the late 16th century, creating a verb specifically describing the process of forming curds. This semantic evolution from a simple noun for a coagulated substance to a verb for the process of coagulation perfectly captures the word's literal meaning, which was later extended metaphorically to describe the clotting of blood or the chilling effect of terror.
Analysis
The word 'curdle' is a simplex verb formed by adding the frequentative or verbal suffix '-le' (from Middle English '-elen', Old English '-lian') to the earlier noun 'curd'. The root 'curd' is of uncertain origin, possibly from a metathesis of 'crud' (Middle English 'crudde', meaning curd or any coagulated substance), which itself is of unknown, possibly Celtic or Germanic, origin.
Examples
The lemon juice caused the milk to curdle.
The sight was so ghastly it made my blood curdle.
If you add acid to hot milk, it will curdle almost instantly.