Motion diagram. A Deaf-recorded clip from the PopSign corpus (CC BY 4.0) exists for this sign and can be placed here.
FROG
“frog”
Hold a fist under your chin and flick the index and middle fingers out twice.
Where the sign comes from
UnknownNo reliable source. We'd rather say so than invent one.
Explained sometimes as a frog's throat pulsing, sometimes as its legs kicking. The sign is well attested; its motivation is not.
No sources — which is the point of the “unknown” tier. If you know of a documented account, the historical databases are where to check it.
The sign, taken apart
Every ASL sign is built from a handshape, a place it's made, and a movement. Learn to see these three and you can read and store any sign.
Starts as a fist with the thumb across the front; ends as index and middle spread, the rest closed.
Also: letter S
Made at the chin.
One-handed.
Repeated. Palm facing left.