to cry, to shout, to howl
虖 centers on loud vocal expression: crying out, shouting, or howling. The meanings all involve a forceful, open-mouthed sound.
虖 combines 虍 (tiger stripes or tiger head) with 乎, which likely contributes the sound and possibly the idea of exhaling or calling out. The exact historical development is uncertain, but the character is associated with vocal sounds like crying or shouting.
The tiger-head enclosure 虍 suggests a fierce, open mouth, and the inner 乎 looks like a breath or sound escaping. Picture a tiger roaring: that's the cry or howl of 虖.
For コ, imagine a tiger letting out a low, guttural 'co' sound as it howls: co -> コ, and the tiger's cry echoes.