1.
first grandchild
One's first grandchild. A word that carries a strong emotional connotation of joy and celebration.
Reading variant
Also read as はつまご. The reading ういまご is traditional and more literary, while はつまご is also common in speech.
Usage
A compound of 初 (first) + 孫 (grandchild). Typically used in happy, celebratory contexts. The prefix 初～ is an old Japanese reading meaning "first" (compare 初陣, first battle).