Somewhat of a rarity, this is a one-word litotes. Because English allows the piling on of multiple affixes, both non- and in- can be prefixed to secure instead of requiring the writer or speaker to say "not insecure."
While technically a double negative, figures of speech and rhetorical devices, especially litotes, are given a certain amount of latitude with regard to the double-negative rule.
Somewhat of a rarity, this is a one-word litotes. Because English allows the piling on of multiple affixes, both non- and in- can be prefixed to secure instead of requiring the writer or speaker to say "not insecure."
While technically a double negative, figures of speech and rhetorical devices, especially litotes, are given a certain amount of latitude with regard to the double-negative rule.