Where does “ճաղ” come from?

ճաղ (Middle Armenian) comes from Georgian ჭალი, from Georgian რჭალი.

Ancestry of “ճաղ”, step by step

Step	Language	Word	Meaning
1	Georgian	ჭალი	rods of a cart/waggon on which a cloth is spread
2	Georgian	რჭალი	—