Why would Lilypond be replacing capital N in lyrics with U+1ECA (Latin Capital Letter I with Dot Below)?

For some reason I can't fathom, every capital N in my lyrics is being replaced with U+1ECA (Latin Capital Letter I with Dot Below). I'm on macos Sonoma 14.6 running Frescobaldi 3.3.0, which calls out to lilypond 2.24.4. What could possibly be causing this?

Here's the source:

\version "2.18.2"  % necessary for upgrading to future LilyPond versions.

#(set-default-paper-size "letter")
#(set-global-staff-size 18)

%\paper {
%  top-system-spacing #'basic-distance = #10
%  score-system-spacing #'basic-distance = #10
%  system-system-spacing #'basic-distance = #10
%  last-bottom-spacing #'basic-distance = #10
%}

global = { \key c \major \time 4/4}

partOneMusic = \relative {
  \clef "treble"
  g'2 f \bar "|."
}
partOneWords = \lyricmode {
Na Na
}
partTwoMusic = \relative {
  \clef "treble"
}
partTwoWords = \lyricmode {
}


pianoRightHandMusic = \relative {
  \clef "treble"
}

pianoLeftHandMusic = \relative {
  \clef "treble"
}

\score {
  <<
    %%{
    \new ChoirStaff <<
      \new Staff = "PartOne" <<
        \set Staff.instrumentName = "PartOne"
        \set Staff.midiInstrument = "piano"
        \new Voice = "partOneVoice" {
          \global
          \partOneMusic
        }
      >>
      \new Lyrics \lyricsto "partOneVoice" {
        \partOneWords
      }
      \new Staff = "PartTwo" <<
        \set Staff.instrumentName = "PartTwo"
        \set Staff.midiInstrument = "piano"
        \new Voice = "partTwoVoice" {
          \global
          \partTwoMusic
        }
      >>
      \new Lyrics \lyricsto "partTwoVoice" {
        \partTwoWords
      }
    >>  % end ChoirStaff
    % %}
    % %{
    \new PianoStaff <<
      \set PianoStaff.instrumentName = "Piano  "
      \new Staff = "upper" <<
        \key d \major 
        \new Voice = "first"
          \relative { \voiceOne \pianoRightHandMusic }
      >>
      \new Staff = "upper" <<
        \key d \major 
        \new Voice = "first"
          \relative { \voiceOne \pianoLeftHandMusic }
      >>
    >>
    % %}
  >>
  \layout { }
  \midi {  }
}

\header{
  title = "WTF?"
  composer = ""
  tagline=""
}

Here's the resulting PDF:

It's a bug in the Times New Roman font shipped by Apple. See also this thread.