I'm presuming plenty of you already realize this, but just to clarify, all of the quotes come from the 36 Lessons of Vivec.
"A Dwemer said, 'We Dwemer are only aspirants to this that the Velothi have. They shall be our doom in this and the eight known worlds, NIRN, LHKAN, RKHET, THENDR, KYNRT, AKHAT, MHARA, and JHUNAL.' The secret to doom is within this Sermon." (From sermon 3)
"At which he stabbed the heart of the City-Face with the Ethos Knife, which is to say RKHT AI AE ALTADOON AI, the short blade of proper commerce. " (From sermon 30)
"Leading the armies of the Chimer was the slave that would not perish, the Hortator Nerevar, who had traded his axe for the Ethos Knife. He slew Dumac at Red Mountain and saw the heart bone for the first time. " (From sermon 36)
"On the ritual of occasions, which comes to us from the days of the cave glow, I can say nothing more than to loosen your equation of moods to lunar currency." (From sermon 35)
"equation of moods to lunar currency" (From sermon 35)
"proper commerce" (From sermon 30)
"RKHET" (From sermon 3)
A brief comment, then.
Ethos refers to the fundamental characteristics of a culture. From sermon 30 (emphases mine):
Now many years had passed in Resdaynia, and the high priests of the Dwemer were building something alike as Vivec and alike as the new Ha-Note of the Grabbers. The Hortator was engaged with an army of theirs that had become too brave, talking foolish words, and Nerevar helped destroy them with the help of the orphan legion of Ayem. When he went to give trophy to Vivec, he saw his lord under attack by the City-Face. The monster was saying this:
'Here we are to replace your city, Vehk and Vehk. We are from the place of the more-than-known emotions, and our citizenry has died from it. Two things we came for, but can stay for only one. Either we ask you to correct our error of culture, or merely take yours by dint of force. The second is easiest, we think.'
Vivec sighed.
'You would replace my direction,' he said. 'I weary of this, though I wanted to kill you an age before. Resdaynia is fallen ill, and I have no time for one more imaginary anology of an unknown incident. Here, take this.'
At which he touched the tower-hope of the City-Face and corrected the error of the Grabbers.
'And this.'
At which he stabbed the heart of the City-Face with the Ethos Knife, which is to say RKHT AI AE ALTADOON AI, the short blade of proper commerce.
The ending of the words is ALMSIVI.
The passage is a comparison of Tribunal-led Dunmeri culture and Dwemer culture (though I suspect the Grabbers might be referencing something else, my guess is pretentious people in the lore forum). The passage is obviously arguing that Dunmeri culture is better.
I forget exactly what RKHT AI AE ALTADOON AI translates too, but its more or less, "the weapon in the hands" or something like that. RKHT is Arkay (as Proweler pointed out) which suggests life and death.
Of course you know why the Dunmeri ethos (culture) is (or is symbolized by) a knife. AE ALTADOON indeed.