Where does “เอกศก” come from?

เอกศก (Thai) comes from Thai เอก, from Pali eka, from Sanskrit एक, from Proto-Indo-Aryan Háykas, from Proto-Indo-Iranian Háykas, from Proto-Indo-European óynos — one; single.

เอกศก (Thai): Lesser Era year whose final figure is one, as...

Definitions

Lesser Era year whose final figure is one, as...

Ancestry of “เอกศก”, step by step

เอกศก traces back through two separate lines of ancestry.

via Thai เอก

Step	Language	Word	Meaning
1	Thai	เอก	sole; single; solitary; one; alone; lonely;...
2	Pali	eka	one
3	Sanskrit	एक	one; alone, solitary, single, happening only...
4	Proto-Indo-Aryan	Háykas	one
5	Proto-Indo-Iranian	Háykas	one
6	Proto-Indo-European	óynos	one; single

via Thai ศก

Step	Language	Word	Meaning
1	Thai	ศก	headhair; era; year
2	Sanskrit	शक	year
3	Old Persian	𐎿𐎣𐎠	Scythia
4	Old Persian	𐎿𐎣	Saka and Scythians, a nomadic people of the Eurasian steppes

Every word from Proto-Indo-European óynos →Every word from Proto-Indo-Iranian Háykas →Every word from Proto-Indo-Aryan Háykas →