Think of the word convert as meaning change, whether it is a person who adopts a new belief, or a changing action, such as when you convert dollars into euros. Many times we can catch a word's meaning by looking at its origins. In this case, the Latin con means around, while vertere means turn..
Maple sap runs best when it freezes at night (e.g. in the high 20-degrees Farenheit range) and then warms up above freezing the next day (in the range of 40-degrees Farenheit and hotter). If it stays warm at night and warm during the day or if it freezes at night but barely goes above freezing the next day, sap does not flow as well or hardly at all.
An immense amount of sap is required to produce maple syrup, because the watery sap must be reduced to achieve the proper consistency and taste. Although the exact amount depends on the sweetness of the sap, in general it takes about 40 times as much maple sap to produce a portion of syrup.