gg5, daij, koj, meikyo
丁々と	72
丁丁と	44

The kokugos describe a different sounds for ちょうちょう and とうとう. I'll draft a separate entry for for とうとう.
This word appears to be rare outside of 丁々発止.
Not a noun.

@@ -3,0 +4,3 @@
+<k_ele>
+<keb>丁々</keb>
+</k_ele>
@@ -8 +11 @@
-<keb>打打</keb>
+<keb>打々</keb>
@@ -11,4 +14 @@
-<keb>丁々</keb>
-</k_ele>
-<k_ele>
-<keb>打々</keb>
+<keb>打打</keb>
@@ -19,5 +18,0 @@
-<r_ele>
-<reb>とうとう</reb>
-<re_restr>丁丁</re_restr>
-<re_restr>丁々</re_restr>
-</r_ele>
@@ -26,4 +21,6 @@
-<pos>&n;</pos>
-<gloss>clashing of swords</gloss>
-<gloss>felling of trees</gloss>
-<gloss>ringing of an ax</gloss>
+<pos>&adv-to;</pos>
+<gloss>(sound of) hitting repeatedly</gloss>
+<gloss>pummelling</gloss>
+<gloss>clashing</gloss>
+<gloss>clacking</gloss>
+<gloss>clicking (e.g. of go stones)</gloss>

All of the refs lead with 丁丁 rather than 打打

Google N-gram Corpus Counts
╭─ーーーーーー─┬───────────┬───────╮
│ 丁丁　　　　 │     3,813 │ 43.2% │
│ 打打　　　　 │     3,839 │ 43.5% │ - adding (daijr/s, koj, etc.)
│ 丁々　　　　 │       507 │  5.7% │
│ 打々　　　　 │       668 │  7.6% │ - adding
│ ちょうちょう │    34,141 │  N/A  │
│ とうとう　　 │ 3,904,747 │  N/A  │
╰─ーーーーーー─┴───────────┴───────╯

@@ -3,0 +4,6 @@
+<k_ele>
+<keb>丁丁</keb>
+</k_ele>
+<k_ele>
+<keb>打打</keb>
+</k_ele>
@@ -8 +14 @@
-<keb>丁丁</keb>
+<keb>打々</keb>
@@ -14,0 +21,2 @@
+<re_restr>丁丁</re_restr>
+<re_restr>丁々</re_restr>