Why is the ninth month called September?
late 14c., hommen "make a murmuring sound to cover embarrassment," later hummen "to buzz, drone" (early 15c.), probably of imitative origin. Sense of "sing with closed lips" is first attested late 15c.; that of "be busy and active" is 1884, perhaps on analogy of a beehive. Related: Hummed; humming. Humming-bird (1630s) so called from sound made by the rapid vibration of its wings.
There is a curious bird to see to, called a humming bird, no bigger then a great Beetle. [Thomas Morton, "New English Canaan," 1637]
mid-15c., from hum (v.).
A low, continuous murmur blended of many sounds.
(from Spanish pepino, "cucumber"), also called Hum (Serbo-Croatian: "hill"), or Haystack Hill, conical hill of residual limestone in a deeply eroded karst region. Pepino hills generally form on relatively flat-lying limestones that are jointed in large rectangles. In an alternating wet and dry climate, high areas become increasingly hard and resistant while low areas are subjected to greater erosion and solution. In some places, such as the Kwangsi area of China, pepino hills may have almost vertical sides and may be riddled with caves. Pepino hills develop to greater heights in regions having subtropical or equatorial rainfall and are then generally called mogotes (Spanish: "hillocks").