Why do we say "A friend in need is a friend indeed"?

Meaning:

Real friends are there for you through good times and bad.

Background:

The earliest known expression of this sentiment is in the writings of Quintus Ennius (239-169 bc), a Roman of Greek descent who is considered by many to be the father of Roman poetry, although only fragments of his writing have survived.

Amicus certus in re incerta cernitur.
A sure friend is known when in difficulty.

There is an inherent ambiguity with this expression depending on whether one spells the ending "indeed" or "in deed."

• A friend in need is a friend indeed (a friend when you are in need is a true friend)
• A friend in need is a friend in deed (a friend who takes action to help you when you are in need is a true friend)

It appears that most people today interpret the expression as "indeed" given that a quick search of Google for "a friend in need is a friend indeed" produced 286 million results, while the alternate spelling produced a mere 30 million, with most of the first pages of results for the latter showing findings for "indeed."

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