Lunar derives from Stellar !

Names of lunar months,
Derive from stellar sources,
Chaitra derives from Chitra,
Aaswina from Aswini.

A Full Moon means,
Sun opposing Moon
When Moon is in Libra, Chitra,
Sun has to oppose in Aries !

During Chaitra, Sun Moon Opposition
Occurs , when Vishu is celebrated
Vishu vakhya sada Chaitre 
Jayathe Mesha Sankrama

The Sacred Viashakha derives
From the Jupiterian VIshakha
When Full Moon in Scorpio
Opposes Sun in Taurus.
( Vaishakhe Vrisha Sankranti)


Sankranti in Sanskrit means,
Solar Ingress in English,
Solstice in Latin,
And Somkran in Thai.

More at

https://www.eastrovedica.com/html/lunarmonths.asp