hem 2 
(hĕm)
(hĕm)n.
A short cough or clearing of the throat made especially to gain attention, warn another, hide embarrassment, or fill a pause in speech.
intr.v. hemmed, hem·ming, hems
Idiom: 1. To utter a hem.
2. To hesitate in speech.
hem and haw
To be hesitant and indecisive; equivocate: "a leader who cannot make up his or her mind, never knows what to do, hems and haws" (Margaret Thatcher).
[From Middle English heminge, coughing, of imitative origin.]