From ọlá ("honour, wealth") + tún dé ("come again"): "honour has returned." Given in the hope the child brings honour to the family, or that a late ancestor's standing is reborn in them. Shortened to Tunde.
Source: Yoruba ọlá- / túndé naming patterns, cross-referenced across wisdomlib (Olatunde), Wikipedia (Olatunji, related), and independent Yoruba-naming guides; túndé "come again" also attested in yorubaname.com (Babátúndé)