Marjorie in Qatar

Yes T'villah is the correct word. Although, in transliterating it, I prefer to drop the initial 'e'. The "vowel" under the first letter, is actually a Shvah which is best described as a "null-vowel" - it does NOT have a sound (Doesn't Arabic have such a "vowel"?). Although it is VERY common to fill in an 'e' when transcribing a Hebrew Shvah to English, it is phonetically incorrect (and I find it annoying ;-)). I've no idea why people insist on doing this. The 'i' vowel is also closer to the 'ee' sound, but not as long. The vagaries of Hebrew/English transcription are amusing.

The idea of being born into a covenant is somewhat alien to Christianity

I can see why Christianity would have everybody entering the covenant baptized. Seeing as historically there are no "native" Christians, it would more sense, initially to just baptize everybody who "comes to Jesus", thus the precedent would be set, and as you say, the covenant is considered much more dependent on individual choice. In Judaism we take the exact opposite approach: The covenant is historical and binding on all Jews for all Time. So someone born a Jew, is bound by this contract, whether they choose to "accept" it or not (this is also why converts are considered 'reborn'). Circumcision is NOT "entering the covenant", so much as putting your signature on the line of an existing contract (or conversely, by putting G-d's "signature" on our flesh, align ourselves with this covenant, by saying that the flesh has a higher purpose in life). If this was not so, then one could "leave" the covenant, merely by not being circumcised. To take things a step further, a Jew also can't leave the covenant by converting to another religion. I could say the Shahadah or be baptized until I was blue, and still be considered as Jewish as ever. No additional act would be required to "revert" back to Judaism.