An enthymeme is a curtailed or truncated syllogism the major or minor term of which is implied, therefore omitted.

The enthymeme [has] either the major or minor premise ... left implied. (Silva Rhetoricae, BYU)

An enthymeme is developed in reverse order as a conclusion paired with a reason: Jon will lie again because Jon has lied in the past. In this example, "Jon will lie again" is the conclusion. It is coupled with the reason "Jon has lied in the past," which is also the minor premise. The major premise is implied and omitted: "Those who lie will lie again."

• Those who lie will lie again.-- Major premise (implied, omitted)
• Jon has lied in the past.-- Minor premise
• Jon will lie again.-- Conclusion

A syllogism has three categorical propositions with major premise, minor premise, conclusion and major term, minor term and middle term.

The major term forms the predicate of the conclusion while the minor term forms the subject of the conclusion. The middle term is not part of the conclusion but is part of each premise: middle term + major term / minor term = major premise / minor premise.

Your set of propositions is a set of three: a major premise, a minor premise and a conclusion. Therefore it cannot be an enthymeme; it must be a syllogism. Let's test this assertion.

The major premise predicate forms the predicate of the conclusion: "test of time." The minor premise subject forms the subject of the conclusion: "Lord Churchill's." The middle term appears in the major premise and the minor premise but it does not appear in the conclusion: "wise." Your set of propositions is a syllogism.

• Wise words stand the test of time.
• Lord Churchill's words were wise.
• Lord Churchill's words will stand the test of time.