suffix
Suffix used in addresses after the name of a company, organization, or department to direct mail to a specific person or section.
株式会社田中商店 気付 山田太郎様
Tanaka Shoten Co., Ltd., c/o Taro Yamada
送り先に「○○気付」と書いてください。
Please write 'c/o XX' on the delivery address.
From 気 (ki, 'attention') + 付ける (tsukeru, 'to attach'), literally 'attach attention', used to direct correspondence to a specific recipient within an organization.