Other forms: humming, hums, hummed
To hum is to sing with your lips shut, so the tune comes out but the words stay in. Someone humming in the shower, a grandmother humming a baby to sleep, you humming the chorus because you have forgotten how the line goes.
Machines hum too: a fridge, a fluorescent tube, a laptop fan, a low steady sound you stop hearing until it stops. As a noun it works the same way, the hum of traffic through an open window, the hum of conversation before a concert. A place can hum with activity, which means it is busy and alive. If you hum and haw, you are hesitating instead of answering. The line to hold on to is that humming has no words, and the moment words appear you are singing.
1verbhumTo sing a tune with your lips closed, making no words.
“She hummed the same three notes all morning without noticing.”
synonyms: croon
2verbdroneTo make a low, steady, continuous sound.
“The old fridge hummed in the corner of the kitchen.”
3verbfullTo be full of activity.
“By nine o'clock the market was humming.”
4nounlowA low, steady, continuous sound.
“There was a faint hum coming from behind the wall.”
From Middle English hummen, which meant to hum, buzz or drone, and also to make a murmuring noise to cover embarrassment. It is kin to Dutch hommelen, to bumble and buzz, and to Middle High German hummen. Nobody borrowed it from anywhere clever: the word is simply an imitation of the sound.
Middle English
hummen — to hum, buzz, drone, make a murmuring sound to cover embarrassment
English, today
hum
From Middle English hummen (“to hum, buzz, drone, make a murmuring sound to cover embarrassment”); akin to Dutch hommelen (“to bumble, buzz”), dialectal Dutch hommen (“to buzz, hum”), Middle High German hummen (“to hum”), probably ultimately of imitative of the sound origin.
Etymology from Wiktionary, CC BY-SA