skull-and-crossbones
UK[ˌskʌl ən ˈkrɒsbəʊnz]US[ˌskʌl ən ˈkrɔːsboʊnz]
n
a picture of a human skull with two crossed bones below it, used as a warning of danger or death, especially on containers of poisonous substances or on pirate flags.
Etymology
the phrase "skull and crossbones" is a descriptive english compound originating in the late 17th or early 18th century. its logic is purely pictorial and symbolic, directly naming the elements of the iconic image: the 'skull' (from old english sculle, meaning the bone framework of the head) and the 'crossbones' (from 'cross,' ultimately latin crux, and 'bones,' from old english bān). the symbol's association with death made it a fitting emblem for pirates, signifying mortal danger, and was later adopted as a universal warning label for poison. the phrase's meaning is therefore not built from classical roots but from a literal description of a culturally established memento mori image repurposed as a stark hazard symbol.
Analysis
this is a fixed compound phrase. it is not productively formed from separable morphemes in modern english but is a lexicalized combination of three words.
Examples
the toxic chemical drum was marked with a prominent skull-and-crossbones.
the pirate ship flew the classic black flag with a white skull-and-crossbones.
modern safety regulations often replace the traditional skull-and-crossbones with more detailed pictograms.