noun
rattlesnake
Refers to the venomous snake known for the rattling sound of its tail.
砂漠でガラガラヘビを見つけた。
I found a rattlesnake in the desert.
Katakana spelling is common and matches usual-kana usage.
Kanji spelling exists but is rarely used; the word is normally written in kana.
From the mimetic word がらがら (rattling sound) and 蛇 (snake). The exact derivation is straightforward; the name imitates the sound the snake makes.