祺
キ, さいわ.い, やす.い

fortunate, blessed, peace of mind, security

JLPT0 G13 S0 F5000

其 here an abbreviated form# of 期 (one full agricultural cycle) + 示 altar/the supernatural → full/abundant blessings from the gods (compare 福 with this same meaning), such as manifested in a rich harvest → *fortunate*; *free of worry*. For the connection between abundance and (good) fortune, compare also 吉.

[Full Kanji Etymology List]