"Omaha" was trending on Twitter during the Broncos' win over San Diego. Omaha, Neb.'s tourism board took notice. It was hard not to, with Peyton Manning barking the snap count directly into CBS's parabolic microphone, and hence your living room.
The short answer is: On any given play, we don't know. If we did, the Chargers and all of Manning's opponents would know too, and it would lose any effectiveness as a cipher. All "Omaha" is is an easily understandable code word that won't be mistaken for anything else, and can be used to signal something that the Broncos have decided ahead of time. How and when Manning assigns the word meaning is yet another example showing he's one of the smartest quarterbacks the sport has ever seen.
Back in October, Fox Sports had a segment with Brian Urlacher and Randy Moss explaining common QB code words. Urlacher identified as something used by his Bears defenses. To him, it simply meant "opposite."
On either side of the ball, it can simply mean "flip the play," either switching from a pass to a run—or pass coverage to run coverage—or going left instead of right, and vice versa. It's a quick and easy way to adjust to what the other team appears to be showing.
But that's not what "Omaha" means to Manning. He used it on 44 of his 70 snaps yesterday, making it unlikely that it was an audible every single time. Instead, he was probably using it as some sort of signal for the snap count. In a 2012 Wall Street Journal article, Richie Incognito identified Tom Brady's use of "Omaha" as a cue to his teammates that the snap was coming.
Said Incognito: "Tom Brady always used to say 'Omaha' and that meant the ball was going to be snapped on 'set-hut.'"
That seemed to be the case much of the time yesterday—Manning's final "Omaha" would be quickly followed by the ball being snapped on "hut." But on a few occasions, "Omaha" then "hut" wasn't the signal—and it made the Chargers jump. On four of San Diego's five neutral zone infractions, "Omaha" immediately preceded a hard count.
When does "Omaha" mean the snap's coming, and when does it indicate a switch to a hard count? Only the Broncos know. Manning likely alerted his offense to the word's meaning on the sideline, or even with a separate code word earlier in the count—it can change from game to game, drive to drive, even play to play.
This is yet another weapon that Manning uses to better effect than almost every other QB. He's a notorious talker at the line of scrimmage, an inveterate user of audibles, and defenses have come to expect and try to anticipate his signals. Much of the time, the verbiage and the gesticulation is meaningless filler, designed to get opponents to start second-guessing their sets. A lot of the time, "Omaha" might just be misdirection. But Manning is a master of giving it meaning just often enough to get defenders to associate it with imminent snaps. And if other teams think they've got "Omaha" figured out, then it's even more powerful when it presages the exact opposite.