"Elves speak [unfamiliar]." And then more muttering.

The muttering probably does mean no osanwë, since they're talking to each other audibly.

"What is [unfamiliar]?" (She's also trying to look it up, of course, but the small problem is that alphabetized lists aren't quite trivial yet because how often does this come up, and the big problem is that spellings are whatever Fëanáro reconstructed them as.)

"Elf-speak [unintelligible] [doesn't seem to be in the phrase book] Elves. [unintelligible.]"

"If I find an Elf, and I say they can't kill you, can they do head talk with you?"

"Elves lie, you say they can't kill you, they kill you."

"Elves can swear not to. I can swear to– to say they can't." Belatedly finding a usable word, "to stop them."

"Can stop Elves?"

"An Elf, yes, not all Elves."

"All Elves." Gestures. Muttering.

"One Elf, captured?" That word's easy to find, probably because of the circumstances around how the Fëanorians got their vocabulary. "Captured, can't kill you."

I might need a volunteer to be tied up and taking orders from me. I'm betting the orcs don't have osanwë the way I don't instead of the way Dwarves don't, so a relay should work, but apparently it's important that the Elf not be able to hurt them.

"Captured Elf talk in heads, hear everything? Swear no Elves kill us?"

"Captured Elf to talk in heads, hear what you say to them. Elves can hear for more, can also swear not to.

Will swear that Elf will not kill you, swear no Elves kill you if you swear to kill no Elves?"

Laughter. "Swear to kill Elves."

"If you swear to kill Elves, Elves will not swear no Elves kill you."

"Then no Elf head read."

"If one Elf swears, using that Elf is same as now."

"Elf say Elf friends kill us."

"Oh. Head speech. Can make the Elf promise to talk to me and you and not Elves while you're here?"

"And then Elves kill us. If Elves kill us either way, no point in helping you first."

"Elves do not kill you if your oaths don't make them. Might be a way out, but I don't have the words to talk about it well enough without using Elf head speech."

"Oath makes us kill Elves."

"Yes, and most orcs are not right now killing Elves. Must be some way to not kill Elves, maybe a way out of the oath."

"Promise no one kill us today, let us go, don't follow. Can kill us if we meet again some other day. Then Elf head-speak."

"If you promise no one finds out you were captured, can you keep that promise?"

"Yes."