同喜 tóngxǐ
[thank you for your congratulation;return one's compliments] 共同欢欣。客套话,用来回答对方的道喜
汉 蔡邕 《上始加元服与群臣上寿表》:“臣妾万国,遐邇大小,一心同欢,同喜逸豫,式歌且舞。”