This was overheard in a conversation. It is a mash up of “breathing down my neck” (closely monitor someone) and “Jump down someone’s throat” (strongly disagree or criticize someone) , with the common word “down” perhaps being the culprit for the conflation. Throats and necks are also situated in the same location so the speaker may have their anatomical parts mixed up. “At each other’s throats” (said of two people who are noticeable angry with each other). might also be in the mix. Certainly this boss closely monitors a little too closely, don’t you think? A shout out to Emily Klingel for hearing this one and passing it on!
Let’s hope not. The speaker was referring to her Mom bugging her about something, and was uttered by the Mistress of Malaphors, Naomi David. It is a congruent conflation of “breathing down my neck” and “up my butt”, both expressions meaning to be closely watching or monitoring someone. Again, mixing body parts and directions often produce malaphors.