One verse

Srimad Bhagavatam 9.13.18

9.13.18

तत: शीरध्वजो जज्ञे यज्ञार्थं कर्षतो महीम् । सीता शीराग्रतो जाता तस्मात् शीरध्वज: स्मृत: ॥ १८ ॥

tatah siradhvajo jajne yajnartham karsato mahim sita siragrato jata tasmat siradhvajah smrtah

tatah
from Hrasvaroma
siradhvajah
a son named Siradhvaja
jajne
was born
yajna-artham
for performing sacrifices
karsatah
while plowing the field
mahim
the earth
sita
mother Sita, the wife of Lord Ramacandra
sira-agratah
from the front portion of the plow
jata
was born
tasmat
therefore
siradhvajah
was known as Siradhvaja
smrtah
celebrated.

From Hrasvaroma came a son named Siradhvaja (also called Janaka). When Siradhvaja was plowing a field, from the front of his plow (sira) appeared a daughter named Sitadevi, who later became the wife of Lord Ramacandra. Thus he was known as Siradhvaja.