conjecture

a guess based on incomplete evidence

Roots

com-: with, together, complete, or intensified
ject: throw or cast

Other words with the ject root

abject: miserable, degraded, or hopeless
conjectural: based on guesswork rather than proof
dejected: sad and low-spirited
eject: to throw out
interject: to throw a remark into a conversation
jettison: to throw away or discard
project: to throw forward; plan or estimate

Con- gives together and ject gives throw. Conjecture throws clues together before proof arrives.

Without the missing data, the explanation remained conjecture.

Conjecture is not random guessing. It is a thrown-together explanation built from clues. The danger is that the pieces may fit neatly before they are true.