conjunctive form (~te form) of the copula なる, expressing a change of state or condition; often used as 'and became' or to connect clauses describing transformation
Analysis. Simple inflection of なる (naru, 'to become'). The ~て form creates a conjunctive or continuous sense: 'became and (then)...' or simply describes the state of becoming.
Dictionary entry by Claude.
Lite mode — plain HTML for e-readers and old browsers. Full version