well

First recorded before 900; Middle English adverb wel, wel(l)e, wil, Old English adjective and adverb wel(l); cognate with Dutch wel, Old High German wela, wola, German wohl, Old Norse vel, Gothic waila; akin to Old English wyllan “to wish,” Latin velle “to wish”; see also will¹

Sometimes an adverb like well is so often placed in front of and combined with a certain past participle in order to modify it that the resulting adjectival combination achieves the status of a common word and is listed in dictionaries. In Dictionary.com you will find, for example, entries for well-advised and well-mannered; for ill-advised, ill-bred, and ill-conceived; and for half-baked and half-cocked. Some of these terms are given full definitions, while others are considered such obvious combinations that you can figure out for yourself what they must mean. It is important to note, however, that compound adjectives like these are hyphenated for use before the noun they modify together. Thus we say that someone is “a well-loved professor,” but there would be no hyphen between well and loved in a sentence like “My English professor is well loved and deserves the award.”
In a similar manner, adjectival compounds formed with better, best, little, lesser, least, etc., are also hyphenated when placed before the noun ( a little-understood theory ), but the hyphen is dropped when the adjectival combination follows the noun ( his films are best known in England ) or is itself modified by an adverb ( a too little understood theory ).
There are exceptions to this pattern. For example, when the combining adverb ends in –ly, no hyphen is required, whether the resulting adjectival combination appears before or after the noun: a highly regarded surgeon; a surgeon who is highly regarded.
Don’t let the hyphens fool you. Punctuation can be tricky!

See good.

First recorded before 900; Middle English noun wel(le), Old English wylle, wella, welle; cognate with German Welle “wave”; Middle English wellen, wel(le), Old English wellan, willan, wyllan; cognate with Dutch wellen, Old Norse vella; both noun and verb ultimately akin to weallan “to boil, bubble up”

See contraction.