A classmate; a fellow student in the same class at school.
Compound from 'class' + 'fellow' (a person associated with another). This older term combines the location 'class' with 'fellow' to create a specific relationship term.
The term 'classfellow' is almost archaic now—we say 'classmate' instead—but it reveals how English creates social terminology, and how different generations had subtly different words for their school companions.
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