Meaning of ~きて~ and ~しまいました in sentence

Question

"あなたの本を車の中に置いてきてしまいました。" means "I left your book in the car." but what is the meaning of "きて" and "しまいました" in context?

Answer 1

「きて」, from 「[来]{く}る」, indicates that it is a "conclusion" of sorts. 「しまう」 indicates a completion, usually with a negative connotation. Taken together, a better translation for the sentence would be "It has come to pass that I have left your book in the car.".

Answer 2

きて is 来て. This is a helping verb which indicates a beginning or continuation of an action up to the present time.

しまいました is the polite past tense of shimau, which indicates a completed action (sometimes with connotations that there are negative consequences, that it should not have been done).

In informal speech V-て/で　しまいました is V-て/で　しまった which is contracted to ちゃった　or じゃった respectively.

For instance "tabeta" is like "ate", but "tabechatta" is like "ate" in the sense of "swallowed": the focus is the completion of the action, not simply eating having taken place in the past. In English, I suppose, we could use "up" for this: tabete-shimau (or tabechau) is something like "eat up".

So you would not say "kinou no o hiru gohan, nani-o tabechatta". This is almost like asking "what did you eat up for lunch yesterday".

The exact nuance is context sensitive.

A parent might say to another: "Hora mite ano ko: zenbu tabechatta!" (Look at that kid, he gobbled up everything.)

As a command:

Ordinary verb, nomu in the -de form: "Nonde!" (Drink!)

With -de-shimau becoming -de-shimatte becoming -jatte: "Nonjatte!" (Drink up! Drink it all!)