The Oracle Bone form of 七 was simply a vertical and horizontal line crossed; however, this shape was too similar to the Oracle Bone script for 甲 (jiǎ) "Armor". A curve was added to the lower half of 七 to differentiate between these two characters.
In Chinese Culture, 七 symbolizes togetherness, and is considered lucky for relationships. Its pronounciation is similar to 起 (qǐ) "Arise", and 气 (qì) "Life Essence". In Buddhism, 七 is related to the concepts of "Holiness" and "Mystery" and is one of the few numbers that are considered lucky in both the East and the West.