What is the full form of the “COCOMO” model?

In software engineering, an estimation model's acronym is usually built by taking the leading letters or syllables of each word in its full, multi-word name, in the exact order those words appear in that name.

The model in question has a standard full name built from three words — Constructive, Cost, and Model — taken in that order. Contracting the first syllable of each of the first two words with the third word gives CO + CO + MO, which reproduces the acronym COCOMO exactly.

• “Cost Constructive Model” swaps the order of the first two words relative to the standard, source-attested name; an acronym contracted from words in this reversed order would not correspond to the name actually used in software-engineering references (e.g., Barry Boehm's cost-estimation literature).

• “Constructive Case Model” replaces “Cost” with “Case,” a word drawn from a different domain (use cases, test cases) rather than the cost/effort-estimation domain this model addresses.

• “None of the above” would apply only if none of the three offered word-combinations reproduced the standard full name — which is not the situation here, since one of them does.

Therefore, the word-combination that exactly reconstructs the acronym COCOMO, in the standard order attested by software-engineering references, is “Constructive Cost Model.”