noun
extremely grateful; deeply moved with gratitude
Emphatic expression combining gratitude and deep emotion. Often used in set phrases like 感謝感激雨霰 (a flood of gratitude).
See also: 感謝感激雨霰
ご支援いただき、感謝感激です。
I am deeply grateful for your support.
彼女からの手紙に感謝感激した。
I was deeply moved with gratitude by her letter.
感激 is deep emotion or being moved, but does not inherently include gratitude; 感謝感激 explicitly combines both.
Compound of 感謝 (gratitude) and 感激 (deep emotion). The exact origin is uncertain, but it likely arose as an emphatic expression combining the two concepts.