“Voilà is used in English to call attention to something, or to present some kind of accomplishment. For example, if you worked all day to plant a beautiful garden, you might present it to the rest of your family with a sweeping arm gesture and an enthusiastic “voilà!” “Viola” clearly doesn’t make sense in this context, but at least senseless violas are better than senseless violins.
“Voilà” is also frequently misspelled in ways that don’t confuse it with another word (but do indicate a mispronunciation). I’ve seen it as wala, wa-lah, wah-lah, and similar variations. Still spelled wrong, but perhaps not as confusing. If you have trouble remembering how to spell “voilà”, remember that it Very Often Isn’t Lettered Accurately.
“To toe the line” figuratively means to conform, submit to authority, obey the rules. The expression started out literally meaning to put your toes against a marked line. It has been used in the discipline of sailors and in sporting events with a starting line among other things. It dates from the 1800s, when “to toe the mark” was also a common expression.
“To tow the line” is not a common expression, but it would mean to drag a rope or something similar behind you.
“It’s barely there” does not mean the same as “it’s barley there”. The former means that something scarcely exists. The latter is pointing out a plant or grain.
For some reason, when a noun is preceded by the indefinite article “a”, people like to delete the space between them and turn them into adverbs or prepositions, for example. It’s a mistake seen frequently with “a part”, but also with other combinations. The most common example of the space elimination trend is “a lot”, but deleting that space doesn’t actually create a new word.
The same problem doesn’t seem to exist with nouns preceded by the indefinite article “an”.
“Fell” is also a noun, a verb, and the past tense of the verb “to fall”, but that is not what gets mixed up here.
To do something in one fell swoop means to do it all at once. One action can accomplish an entire task. The noun swoop dates from the 1540s, and represents the action that a bird takes when pouncing on its prey. One fell swoop—one deadly pounce—meant that the prey was caught in one shot. No need for further attempts.
Abdicating is an action that a person chooses to do, and that person is very likely an adult. It is not an action that is done to you. So if you see a sentence that says that the boy was abdicated, it is a safe bet that abducted was meant.