Sorting dataframe by number of occurrences of factor

Apologies for what's probably quite simple, but I'm having some problems with
sorting a data frame by the number of occurences of each level of a factor.

df<-data.frame(id=c(1:20),name=c('a','b','b','c','a','d','b','e','d','d','c','a','b','a','a','b','f','b','c','g'))

I want to sort the dataframe so that the values of df$name that occur most
often are at the bottom - ie. in the order:

attributes(sort(summary(df$name)))$name = "e" "f" "g" "c" "d" "a" "b":

sort(summary(df$name))

e f g c d a b 
1 1 1 3 3 5 6 

So the desired result is:

id name
8    e
17    f
20    g
 4    c
11    c
19    c
 6    d
 9    d
10    d
  1    a
  5    a
12    a
14    a
15    a
  2    b
  3    b
  7    b
13    b
16    b
18    b