From the Letter to the Hebrews, chapter two, verse seventeen:
Unde débuit per ómnia frátribus similári, ut miséricors fíeret et fidélis póntifex in iis, quæ sunt ad Deum, ut repropitiáret delícta pópuli.
similari is from similo, similare, similavi, similatus
to imitate, to copy, to look like
When the infinitive ending are is replaced with ari, it becomes a passive infinitive: to be imitated, to be copied.
The RSV translates thus: Therefore he had to be made like his brethren in every respect, so that he might become a merciful and faithful high priest in the service of God, to make expiation for the sins of the people.
Christ became like us in all things but sin. During the Christmas season the Church ponders two great truths and holds them together, that He is truly God, and truly man. They seem incompatible, like repelling magnets, yet this is the truth of the mystery of God’s Incarnation: He remains God, yet He became like us.
The sense of the word similari seems to be to be like.
We find the same root word in Matthew 6:8, when Christ says, Nolite ergo assimilari eis : scit enim Pater vester, quid opus sit vobis, antequam petatis eum. / Therefore do not imitate them : for your Father knows what you need before you ask Him.
And in Isaiah 40:25, Et cui assimilastis me, et adæquastis ? dicit Sanctus. / To whom then have you compared me, and made me equal? says the Holy One. Bearing in mind the Hebraic use of parallelism, we infer a similarity of meaning between made me equal and compared.
Then there is this verse from Song of Songs 8:14 for which be like seems a good translation: Fuge, dilecte mi, et assimilare capreæ, hinnuloque cervorum super montes aromatum.
In connection with all this, I cannot help but think of Star Trek: The Next Generation, not, as you might understandably imagine, because Captain Jean Luc Picard’s Borgish name was Locutus*, one of that series’ many allusions to the Latin language, but rather because in connection with the Borg’s insatiable appetite for new membership, the good reader will recall a catch-phrase whose root, ultimately, is the very word in question: “Resistance is futile. You will be assimilated into the Borg.” A treasury of English words are derived therefrom: similar, similarity, simulate, similitude, verisimilitude, assimilate.
* Translation: The man having spoken.