leftfield

Left field is the area of a baseball diamond beyond third base, and the player who covers that territory.

From this comes the expression out of left field, describing something unexpected, unconventional, or seemingly random—perhaps because a throw from left field arrives from an unexpected direction.

As an adjective, often hyphenated or written as one word, leftfield characterizes ideas, art, or approaches that are unconventional or experimental: Their leftfield sound doesn't fit neatly into any genre.