diff --git a/NEWS.md b/NEWS.md
index 0f7da3162e200..46fa26c0721c7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -740,6 +740,9 @@ Deprecated or removed
 
   * `num2hex` and `hex2num` have been deprecated in favor of `reinterpret` combined with `parse`/`hex` ([#22088]).
 
+  * `copy!` is deprecated for `AbstractSet` and `AbstractDict`, with the intention to re-enable
+    it with a cleaner meaning in a future version ([#24844]).
+
   * `a:b` is deprecated for constructing a `StepRange` when `a` and `b` have physical units
     (Dates and Times). Use `a:s:b`, where `s = Dates.Day(1)` or `s = Dates.Second(1)`.
 
@@ -766,7 +769,7 @@ Deprecated or removed
     in the new `Unicode` standard library module ([#25021]).
 
   * The aliases `Complex32`, `Complex64` and `Complex128` have been deprecated in favor of `ComplexF16`,
-     `ComplexF32` and `ComplexF64` respectively (#24647).
+    `ComplexF32` and `ComplexF64` respectively ([#24647]).
 
   * `Associative` has been deprecated in favor of `AbstractDict` ([#25012]).
 
diff --git a/base/abstractdict.jl b/base/abstractdict.jl
index e8f42bb2c5a53..5264f002a9e99 100644
--- a/base/abstractdict.jl
+++ b/base/abstractdict.jl
@@ -230,15 +230,6 @@ function merge!(combine::Function, d::AbstractDict, others::AbstractDict...)
     return d
 end
 
-# very similar to `merge!`, but accepts any iterable and extends code
-# that would otherwise only use `copy!` with arrays.
-function copy!(dest::Union{AbstractDict,AbstractSet}, src)
-    for x in src
-        push!(dest, x)
-    end
-    return dest
-end
-
 """
     keytype(type)
 
diff --git a/base/array.jl b/base/array.jl
index 0e1ffaa91a27f..04b3e90b37be6 100644
--- a/base/array.jl
+++ b/base/array.jl
@@ -585,7 +585,12 @@ function grow_to!(dest, itr, st)
             push!(dest, el::T)
         else
             new = similar(dest, typejoin(T, S))
-            copy!(new, dest)
+            if new isa AbstractSet
+                # TODO: merge back these two branches when copy! is re-enabled for sets
+                union!(new, dest)
+            else
+                copy!(new, dest)
+            end
             push!(new, el)
             return grow_to!(new, itr, st)
         end
diff --git a/base/deprecated.jl b/base/deprecated.jl
index 860f839acce0a..b617ec96ff0dd 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -3184,6 +3184,10 @@ info(io::IO, err::Exception; prefix="ERROR: ", kw...) =
 info(err::Exception; prefix="ERROR: ", kw...) =
     info(STDERR, err, prefix=prefix; kw...)
 
+# #24844
+@deprecate copy!(dest::AbstractSet, src) union!(dest, src)
+@deprecate copy!(dest::AbstractDict, src) foldl(push!, dest, src)
+
 # issue #24019
 @deprecate similar(a::AbstractDict) empty(a)
 @deprecate similar(a::AbstractDict, ::Type{Pair{K,V}}) where {K, V} empty(a, K, V)
diff --git a/base/dict.jl b/base/dict.jl
index 692d5377ae08e..840077d9e51fa 100644
--- a/base/dict.jl
+++ b/base/dict.jl
@@ -180,7 +180,7 @@ function grow_to!(dest::AbstractDict{K,V}, itr, st) where V where K
             dest[k] = v
         else
             new = empty(dest, typejoin(K,typeof(k)), typejoin(V,typeof(v)))
-            copy!(new, dest)
+            merge!(new, dest)
             new[k] = v
             return grow_to!(new, itr, st)
         end