pa-, -redup, mag-, mag--redup
To screw up one's face (as when in pain or when whining).
Reduplication is an amplification of the strain in one's face.
That child is starting to screw up his face because he wants to nurse.
That woman is really screwing up her face because of the pain in her stomach.
Man sini' gi anak-anak naa magsangngi'-sangngi' ni kalingantu na.
Since earlier today that child has been screwing up his face because he is hungry.