Figura etymologica is a rhetorical figure in which words with the same etymological derivation are used in the same passage.
Examples in modern English are the phrases "might and main" (both of which are derived from the Proto-Indo-European root megʰ-) and "chai tea", in which both come from words for tea (cha and te) in different Chinese dialects.
The figura etymologica has both a narrower and a broader definition.
In the narrower definition, it is restricted to the use of the accusative with cognate verbs (for example, live a good life, sing a long song, die a quiet death).
In the broader definition, the figura etymologica refers to just about any sort of repetition of cognate words relatively close to each other.